Association of health-risk behaviors with perceived academic performance among middle and high school students: A cross-sectional study in Shanghai, China

Adolescence is a susceptible period to establish health-risk behaviors, which may have an impact on academic performance. The aim of this study was to investigate the association between health-risk behaviors (HRBs) and perceived academic performance (PAP) of adolescents in Shanghai, China. The data of the present study included three-round Shanghai Youth Health-risk Behavior Survey (SYHBS). This cross-sectional survey investigated multiple HRBs of students involved in dietary behaviors, physical activity and sedentary behaviors, intentional and unintentional injury behaviors, and substance abuse behaviors, as well as PAP by using self-reported questionnaire. Using a multistage random sampling method, 40,593 middle and high school students aged 12 to 18 years were involved. Only participants with complete data on HRBs information, academic performance and covariates were included. A total of 35,740 participants were involved in analysis. We used ordinal logistic regression to analyze the association between each HRB and PAP adjusting for sociodemographic, family environment and duration of extracurricular study. The results showed that students who did not eat breakfast or drink milk everyday were more likely to have a lower PAP, with a decreased odds of 0.89 (95%CI: 0.86–0.93, P<0.001) and 0.82 (95%CI: 0.79–0.85, P<0.001), respectively. The similar association was also found in students who did exercise ≥60 minutes for less than 5 days/week, spend time on watch TV beyond 3 hours/day and other sedentary behaviors. Most intentional and unintentional injuries, and ever smoked were associated with a lower PAP. Our finding suggests that multiple HRBs negatively associated with PAP of adolescents. It needs to raise public health concerns with HRBs in adolescents, and to develop and implement comprehensive interventions on HRBs.

Introduction China, Shanghai Municipal Center for Disease Control and Prevention (SCDC) has carried out the Shanghai Youth Health-risk Behavior Survey (SYHBS) to monitor HRBs among middle and high school students aged 12 to 18 years in Shanghai since 2004. In present study, three-round data of SYHBS were aggregated for analysis. We aimed to investigate the potential association of each HRB and academic performance among middle and high school students in Shanghai, and to provide evidence for education and health departments to develop early prevention strategies, programs, and interventions for adolescents. If HRBs are related to academic performance, there is important significance for local education and health departments to carry out health promotion regarding HRBs within communities, schools, and families.

Sample and setting
The SYHBS was an anonymous cross-sectional survey of middle and high school students from grade 6 to 12 in Shanghai. It was conducted every two to four years. We adopted multistage random sampling by dividing the schools in each district into two strata, middle school and high school, based on the educational levels. According to the proportion of students in each district of Shanghai, probability proportional to size (PPS) sampling was adopted in each stratum to select schools. Then, the classes were randomly sampled in each grade of the selected schools. All students in the selected classes were required to filled out the questionnaire anonymously.
In this study, we analyzed the data in 2004, 2012, and 2019, including a total of 40,593 middle and high school students. Only participants with complete data on HRBs information, academic performance and covariates were included, with a sample of 35,740 students. The study has been approved by the Ethics Committee of SCDC (2022-1). We got permission from each school. All school principals provided written informed consent before the surveys.
Procedures. The SYHBS was initiated by SCDC and implemented by the CDC in 16 districts in Shanghai [20,23]. Each District Departments of Education supported the launch of surveys in middle and high schools in Shanghai. Survey investigators included school health professionals from SCDC and 16 district level CDCs in Shanghai, who were underwent unified training. The information filled in by the students was kept strictly confidential.
Measures. The questionnaire adopted was Shanghai Youth Health-risk Behavior Survey Questionnaire (SYHBSQ), which has a test-retest reliability of 0.93 [24]. SYHBSQ consisted of basic demographic information (age and gender), the HRBs, academic performance, family environment (maternal education and family structure), and duration of extracurricular study.
In current study, the concerned HRBs consisted of four dietary behaviors, four physical activity and sedentary behaviors, four unintentional injuries, nine intentional injuries, and four substance abuse behaviors. The dietary behaviors involved eating breakfast, drinking milk, drinking soda, and eating dessert. The physical activity and sedentary behaviors included the spending time on doing exercise, watching TV, surfing the Internet, and video game. The unintentional injuries referred to jaywalking, cycling violations, swimming in unsafe regions, and severely injured. The intentional injuries included physical fight, feeling unsafe on the way to school, being bullied, feeling lonely, academic stress, insomnia, feeling depressed, and run away from home. Substance abuse behaviors involved tobacco smoking and alcohol drinking. Table 1 presented each HRB description and coding for analysis.
Perceived Academic Performance (PAP) was assessed by a single-item measure, "How would you rate your overall academic performance compared with classmates?". Students could select one of the following response options: poor, below average, average, above average, good, and not sure.
We selected covariates which were potentially related to HRBs and academic performance. Covariates included student's gender (male or female), maternal education (elementary school and below, middle school, high school, junior college; bachelor's degree and above), family

Data analysis
We entered data with Epidata 3.1 and analyzed data by SPSS 25.0 software package (IBM, Armonk, NY). The distribution of each HRB among study population was present with a composition ratio (%). The Chi-square test was used to compare the distribution of PAP with different sociodemographic characteristics. Finally, we performed ordinal logistic regression to examine the association between each HRB and PAP in crude model and adjusted model, respectively. A P value < 0.05 was statistical significance. Table 2 describes the population characteristics and response rates in 2004, 2012, and 2019, respectively. The number of respondents in each survey in this study was the same size calculated according to the sampling method and the behavior prevalence. The sample sizes of the individual surveys in the three years were 8,597, 18,820, and 13,176, respectively accounted for 1.03%, 3.21%, and 2.36% of the total number of middle and high students in Shanghai. The response rates for the three surveys were 92.22%, 92.24%, and 97.75%, respectively. The average age of the students in this study was 14.9±1.9. The distribution of students with poor PAP, below average PAP, average PAP, above average PAP, and good PAP were found in a total of 2,940 (8.23%), 6,856 (19.18%), 11,060 (30.95%), 9,984 (27.94%), and 4,900 (13.71%), respectively. As shown in Table 3, significant differences in age, gender, school type, family structure, maternal education, extracurricular study time, and survey year were found in students with different PAP. Table 4 reports the prevalence of each HRB among adolescents from the lowest rate of currently smoking (2.4%) to the highest rate of academic stress (81.7%). Table 5 reports the OR of the association between HRBs and students' PAP adjusted by age, gender, school type, family structure, maternal education, extracurricular study time, and survey year.

Association between health-risk behaviors and perceived academic performance
Dietary behaviors. In the crude analyses, ate breakfast or drank milk on all 7 days was associated with PAP. Students who did not eat breakfast or drink milk on all 7 days tended to have a lower PAP, compared with students who ate breakfast or milk on all 7 days (P<0.001). After adjusting for all covariates, these association were also significant with the decreased  Intentional injuries and unintentional injuries. We found that except for feeling unsafe on the way to school and insomnia, most of intentional injuries and unintentional injuries were associated with PAP. The effect was stronger for academic stress than other behaviors, with the adjusted decreased odds of 0.79 (95%CI: 0.75-0.84, P<0.001). On the other hand, feeling lonely in the past 12 months was positively associated with PAP, with an increased odds of 1.11 (95%CI:1.06-1.16, P<0.001) in the adjusted model. Substance abuse behaviors. After adjustment, results showed that students who ever smoked as compared to their counterparts were less likely to have a higher PAP (OR:0.85, 95% CI:0.80-0.91, P<0.001). Other substance abuse behaviors were not found to be associated with PAP.

Discussion
The present study examined the association between student's PAP and HRBs involved in diet, physical activity and sedentariness, intentional and unintentional injuries, and substance abuse, with a sample of 12-18 year old Chinese adolescents in Shanghai. We found that students who had HRBs were more likely to present a lower PAP, compared to those who adopted health behaviors. The results indicated that students who had not eaten breakfast on all days per week was a risk factor for lower PAP. It is consistent with previous systematic review demonstrating that habitual breakfast pattern is positively correlated with students' academic performance [25]. A UK study reported that academic performance decreased with lower frequencies of school-day breakfast consumption in adolescents [26]. Breakfast was believed to be the most important meal of the day, which contributed to 25%-30% of total daily energy [27]. With the increase in breakfast frequency, energy level throughout the day and levels of protein, calcium, iron, zinc, selenium, retinol, and other nutrients consumed significantly increased. Some of these nutrients play an important role in brain development and cognitive levels of learning [28]. Those who skipped breakfast might have lower blood sugar levels, resulting in reduced cortical excitability and difficulty concentrating [29]. On the other hand, studies have shown that motivation to learn mediates the relationship between breakfast consumption and academic performance [30]. Thus, students who do not eat breakfast might decrease alertness and motivation in class, and thereby affect their performance.
We also found that students who participated in long-term physical activities or spent shorter hours on screen media are apt to get good PAP, compared to their counterparts. Several reviews have shown that physical activities improve the academic performance of children and adolescents. A study showed that the relationship between physical activity and academic performance was mediated through cognition-that is, physical activity promoted cognitive development in children, showing a positive impact on academic performance [31]. A Japanese study also showed that children who participated in more physical activities and spent less time looking at screens had better academic performance than children who were less engaged in less physical activities and more engaged with screens [32]. A study conducted on Chinese adolescents reported that spending more time on television, videos, and social networking sites were negatively associated with academic performance [18]. Screen exposure (especially TV-viewing) is a passive behavior required little intellectual input. The prolonged video screen use may stimulate impulsive behavior and cause attention deficits, adversely affecting children's intellectual development and cognition [33]. Unintentional injury is a risk factor of lower PAP. It always accompanied with sickness absenteeism and disability. An India cross-sectional study shown that the sickness absenteeism of unintentional injuries averaged over one week, and about half of injured children missed school after an injury [34]. Students who are more frequently absent from school have missed teacher-led lessons, peer interactions, and other learning activities, and are consequently likely to obtain lower academic performance [35][36][37]. With regard to intentional injury, we found that psychological health problems including internalizing and externalizing behaviors were negatively associated with academic performance. These findings are consistent with other studies, for example, symptoms of depression have negative effect on students' attention and memory [38,39]. A study in the UK reported that depression predicted a decline in examination performance [40]. Moreover, studies aimed at undergraduate students supports that academic stress is an impediment to academic performance, [41][42][43] although there were few study focused on the association between academic stress with academic performance in adolescents. A moderate level of academic stress helps to increase academic self-efficacy and obtain better educational outcomes [42]. However, once students experienced high stress levels beyond their load-bearing potential, it could result in school burnout and worse performance [43]. Regarding externalizing behaviors (physical fight and bullying), several studies are consistent with our findings. A study conducted on American high school students showed that a low self-perception of academic performance was associated with being involved in a physical fight [44]. A Spanish study reported that students in the role of the bully/victim had lower academic performance, compared with those in non-bully/non-victim [45]. Bullying has a dual direction, such that being bullied may lead to future aggressive behaviors [46]. Exposure to physical fight or bullying situations affected students' perceptions of safety and belonging at school, harmed social relationships, and caused difficulties in academic perform and dropping out of school [47,48]. For substance abuse behaviors, our results indicated that students who had ever tried cigarette smoking tend to present lower academic performance. Animal studies have shown that nicotine has effects on deficits in cognitive function and emotional dysregulation in adolescent mice [49]. In addition, students with poor academic performance are more susceptible to cigarette smoking [50]. A study in South Korea found that students with poor academic performance are at higher risk of smoking than those with good academic performance [51]. Therefore, smoking is likely to push students into a vicious cycle of poor academic performance.
The main strength of our study is the first large population-based study that has examined possible association of HRBs with PAP through a well-designed survey among adolescent students in Shanghai, China. In addition, the investigation contained comprehensive domains of HRBs. This study also has several limitations. Firstly, this was a cross-sectional study, with the data from a given time point, which cannot determine the causal relationship (if any) between HRBs and academic performance among middle and high school students. Secondly, the collected data from self-reported questionnaires tend to be subjective, although the questionnaires were generally confirmed to be reliable in the test-retest reliability analysis. The presence of recall bias also should not be ignored. Finally, this study only analyzed the association between each HRB and PAP. Further study is needed to focused on clustering and cooccurrence of HRBs among adolescents.

Public health implication
The results of this study suggest that, in addition to students' academic performance, parents and educators in schools should concern about the multiple HRBs in adolescents. Based on these findings, we recommend effective interventions during adolescence. It is an opportunity to rectify health problems that have arisen during childhood, form a healthy lifestyle, and prevent adolescents from undermining health in adulthood [11]. We should strengthen the collaboration between schools, families, and communities to push forward health promotion programs directed toward HRBs including but not limited to promoting regular breakfast intake projects, improving students' nutritional status, enriching extracurricular activities, and managing screen time. In addition, schools and families should promote health education to increase the students' awareness of unintentional injuries, and pay more attention to mental status of students to avoid intentional injuries.

Conclusions
In conclusion, HRBs were significantly associated with PAP among adolescents in Shanghai. Students who had irregular breakfast, spent less time on physical activity and more time on exposure to the screen, and experienced intentional/non-intentional injuries were more likely to have a lower academic performance. Our findings highlight the requirement to pay special attention to the students who had multiple HRBs.